/* use of the center keyword */
digraph G {
	graph [center=1 rankdir=LR bgcolor="#808080"]
	edge [dir=none]
	node [width=0.3 height=0.3 label=""]
	{ node [shape=circle style=invis]
		1 2 3 4 5 6 7 8  10 20 30 40 50 60 70 80
	}
	{ node [shape=circle]
		a b c d e f g h  i j k l m n o p  q r s t u v w x
	}
	{ node [shape=diamond]
		A B C D E F G H  I J K L M N O P  Q R S T U V W X
	}
	1 -> a -> {A B} [color="#0000ff"]
	2 -> b -> {B A} [color="#ff0000"]
	3 -> c -> {C D} [color="#ffff00"]
	4 -> d -> {D C} [color="#00ff00"]
	5 -> e -> {E F} [color="#000000"]
	6 -> f -> {F E} [color="#00ffff"]
	7 -> g -> {G H} [color="#ffffff"]
	8 -> h -> {H G} [color="#ff00ff"]
	{ edge [color="#ff0000:#0000ff"]
		A -> i -> {I K}
		B -> j -> {J L}
	}
	{ edge [color="#00ff00:#ffff00"]
		C -> k -> {K I}
		D -> l -> {L J}
	}
	{ edge [color="#00ffff:#000000"]
		E -> m -> {M O}
		F -> n -> {N P}
	}
	{ edge [color="#ff00ff:#ffffff"]
		G -> o -> {O M}
		H -> p -> {P N}
	}
	{ edge [color="#00ff00:#ffff00:#ff0000:#0000ff"]
		I -> q -> {Q U}
		J -> r -> {R V}
		K -> s -> {S W}
		L -> t -> {T X}
	}
	{ edge [color="#ff00ff:#ffffff:#00ffff:#000000"]
		M -> u -> {U Q}
		N -> v -> {V R}
		O -> w -> {W S}
		P -> x -> {X T}
	}
	{ edge [color="#ff00ff:#ffffff:#00ffff:#000000:#00ff00:#ffff00:#ff0000:#0000ff"]
		Q -> 10
		R -> 20
		S -> 30
		T -> 40
		U -> 50
		V -> 60
		W -> 70
		X -> 80
	}
}
